Week - 4 - 2D meshing for Plastic components

Aim:

To generate mid surface for the given Plastic Bottle Cap model after checking & verifying the geometrical errors and do 2D meshing on the generated mid surfaces that satisfies the given Quality criteria.

Procedure:

Since all the components in the model have thickness less than 5mm, 2D meshing can be done. The detailed procedure for completing the FE Model is mentioned in the following paragraphs.

Import Geometry:

Go to File > Open > Select file to import

Topology clean-up:

• Initially when the model is opened, perform Checks > Geometry on the component to make sure there are no irregularities present. If any errors occur, we can use Auto fix to solve them or do it manually by using various commands in the Topo deck.
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• After the geometry check is done, Measure command is used to estimate the thickness of the components.
• At times when some of the features are not appearing in their original form, the Auxiliaries > Fine command can be used to increase the resolution at that particular area and check the original shape of the feature.
• Then, the Faces > Orientation command is performed to make sure that all the faces are in same orientation (i.e., positive or negative).

Mid-surfacing:

• To create the mid-surfaces, Faces > Middle command can be used as it automatically considers the thickness of the component.
• The surfaces which are perpendicular to each other or the surfaces that needs to be connected in some sort of T-shaped manner can be connected to each other by using the Faces > Extend and Intersect options.
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• We can approach those areas having varying thickness in 2 different methods. First way is to create middle curves and then creating a new surface using the generated middle curves. In the second approach, we can create multiple surfaces that could potentially capture the parent geometry.
• Thickness can be assigned by either spliting the surface into various parts and assigning the thickness according to the varying thickness of the parent geometry or by assigning the average thickness of the parent geometry.
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• The Faces> Topo command can be used to make sure that all the adjoining mid-surfaces are stitched together.
• For identical/repetitive surfaces, Transform > Copy is used to replicate the generated mid-surface.
• To remove symmetric surfaces, use Faces > Rm.Dbl.
• After generating mid-surface for all the components, individual PIDs for the different thickness components are created.
• Geometry check can be performed once again to eliminate any errors that are present.
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Define Quality Criteria:

Press F11 to open Quality criteria window. Then, Select and define the required criteria.

Meshing:

• Open Mesh parameters and enter appropriate values.
• For meshing the surfaces, Use Best Mesh algorithm from the Mesh generation panel.
• Always start meshing from the features.
• To view the mesh quality, Toggle Hidden mode.
• Use Shell mesh > Reconstruct to reform the mesh elements.
• Use Shell mesh > Smooth to smoothen the mesh element structures.
• To copy the mesh generated on the features to other identical features, use Transform > Copy (delete the unmeshed identical features before using Copy option since it'll copy along with the geometric surfaces).
• Perform Topo after copying.

Some of the basic conditions to be kept in mind while meshing are as follows:

• No Tria elements should be present at the perimeter and the holes.
• No Tria elements should be connected back-to-back or present opposite to each other.
• No Tria elements should be on the features and fillets.
• Max no. of elements should be perpendicular to each other (Minimise wavy mesh flow patterns).

Mesh Flow Correction:

• Use Elements > Split command to move the Tria elements forward.
• Use Elements > Swap command to move the Tria elements sideward.
• Use Grids > Paste command to move the Tria elements backward.
• After meshing, Reconstructing & smoothing operation are completed, Use Macros > Join (change Reconstruct to Keep in options list).
• Stitch all the independent feature meshes using Paste option.
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Learning Outcomes:

• Gained better fluency with the ANSA GUI.
• Acquired aptitude on identifying and improving failing and bad quality elements.
• Became familiar with various ANSA commands like Faces > Middle, Intersect, Extend, Split, Swap, Paste, Origin, Smooth, Reconstruct, Cut, Edge2Perimeter, etcetera.
• Learnt to create and edit curves using Cons2curves, Curve > Connect and Curve > Middle options.
• Became familiar working with Triple cons.

Conclusion:

Thus, the given Bottle Cap model is meshed with 2D meshing technique satisfying the required Quality criteria by following all the necessary procedure.